AGE-DEPENDENT DECLINE OF DOPAMINE D1 RECEPTORS IN HUMAN BRAIN - A PETSTUDY

Radioligand binding studies in animals have demonstrated age-related l oss of dopamine receptors in the caudate and putamen. In humans, while age-related declines in dopamine D2 receptors have been consistently reported, the effects of ageing on D1 receptors have been controversia l. We used positron emission tomography (PET) with [C-11]SCH 23390 to investigate dopamine D1 receptor binding in 21 normal volunteers aged 22-74 years. We also assessed their motor function with a Modified Col umbia Score (MCS) and the Purdue Pegboard Test (PPBT). D1 binding pote ntials were derived using a graphical analysis with a cerebellar tissu e input function. Standard linear regression techniques were used to d etermine the age-related rate of decline of D1 binding. We found an ag e-dependent decrease of D1 receptor binding in the caudate (6.9% per d ecade) and putamen (7.4% per decade). There was also a significant inv erse correlation between [C-11]SCH 23390 binding in the occipital cort ex and age (8.6% decline per decade). PPBT score also decreased with a ge (P = 0.007). There was a direct correlation between PPBT score and D1 binding potential. We conclude that dopamine D1 receptor density de clines with age and that the effects of physiological ageing may play a role in the expression of extrapyramidal disorders in the elderly. S ynapse 30:56-61, 1998. (C), 1998 Wiley-Liss, Inc.dagger